When the conquistador, Hernan Cortes, arrived in Tenochtitlan in 1519, he saw gardens floating on the surface of Lake Texcoco. At the time, the basin of Mexico was characterized by an interconnected system of ponds and lagoons. Hundreds of floating gardens dotted the maze-like waterways around the lake.
The Aztecs called the gardens chinampas. Cortes and his men later learned that the Aztecs had built the little islands out of mud and cane. They grew vegetables, maize, and amaranth on the raft-like structures.
Thousands of Aztecs relied on chinampas for food across the Mexican wetlands. Some of the floating gardens had roots reaching deep into the muddy lake floor.
Hydroponics + Aquacultrure = Aquaponics
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Combining hydroponics with aquaculture, the modern aquaponics system operates on a principle similar to that of the Aztec chinampa.
The basic premise is that the waste produced by fish feeds plants. Plants clean the water for the fish, creating a small, self-contained ecosystem.
Starting an Aquaponic Garden
Starting an aquaponic garden involves some work. But once you have the system started, an aquaponic garden requires little in the way of maintenance.
Here’s how to set up a media-based aquaponics system that will allow you to grow your own food.
1. Build your fish tank.
Just like keeping an aquarium, you’ll need to follow all the safe practices of fishkeeping. Your fish will require a certain amount of space. The species of fish you decide to raise will determine the size of the tank you’ll need.
You might be able to repurpose a small aquarium or a standard 20-gallon fish tank for smaller fish. However, most people choose to use large barrels or food-grade containers with opaque sides. You’ll find many good options for both types of containers online.
Be sure to get a pump to draw water from the tank to the grow bed and back again. For our tests, we rigged a PonicsPump Submersible Pump for two 25-gallon tanks. We were quite pleased with its performance.
For bigger tanks, experts recommend using an air pump to push oxygen into the water, as well.
You’ll need to set up the tank as you would a standard fish tank. That means you have to dechlorinate the water before you add the fish. To do this, simply allow the water to cycle for about 4 to 6 weeks.
This gives the bacteria time to build up. The bacteria will then break down the ammonia and nitrites present in the water. This process, in turn, will produce the nitrates that will feed your plants.
2. Build your media bed.
You’ll need a container for your plants, too. This will be your system’s media bed. You can use a large heavy-duty plastic tray or a wooden pallet crate. You may need to raise the bed on top of a stand that can carry its weight.
Once you’ve rigged your media bed into place, you’ll need to fill it with your chosen media. We use Organic Gardening Clay Pebbles for our aquaponic system. Clay pebbles -or hydrotons – are pH neutral. They don’t affect the water. They also hold moisture well.
The website, Earth Easy, suggests a size ratio of 1:1 between the fish tank and grow bed. That means equal volumes for each.
3. Add the fish.
Once your tank has cycled properly, you can add the fish. Experts say certain species of fish have proved particularly adaptable to aquaponics. The most common choices include the following:
- Tilapia are easy to grow, simple to care for, and hardly ever fall to disease.
- Goldfish produce a lot of waste, which makes them ideal for aquaponic systems.
- Koi and ornamental fish like guppies, tetras, and mollies are valued by fish enthusiasts.
- Some farmers raise catfish, carp, silver perch, and barramundi in their aquaponic systems, as well.
4. Add the plants.
Experts recommend leafy plants for aquaponics setups. These plants tend to grow well in soil-less systems. But, with enough fish, you may be able to grow fruiting plants such as peppers and tomatoes, too.
Below are the plants we recommend for your system.
- Basil
- Kale
- Lettuce
- Mint
- Watercress
Those with heavily stocked and well-established aquaponic systems might be able to grow bigger plants. These may include the following:
- Beans
- Cabbage
- Cauliflower
- Cucumbers
- Squash
- Tomatoes
- Peas
- Peppers
- Strawberries
Experts recommend that you plant seedlings. This will allow your garden a head start. Just gently plunge the roots into the pebbles. Make sure they reach deep enough into the medium to draw nutrients from the water that will pass through.
5. Maintain your aquaponic ecosystem.
Maintaining an aquaponic system is easy and simple. You’ll need to feed your fish a quality diet. You can use simple flake food and give them the occasional treat.
We feed the goldfish in our system Tetra Goldfish Flakes. The fish seem to love the stuff. Only feed your fish as much as they can eat in around five minutes, two to three times a day.
Be mindful that you don’t introduce any diseases to the tank. This is why we advise against adding any live food for the fish.
You’ll need to test the water in the tank every week or two. Check the pH, ammonia, nitrites, and nitrate levels. For this, you’ll need a water test kit.
We favor the API Freshwater Master Test Kit. The kit monitors the five most vital water parameter levels in freshwater aquariums. These are the pH, high range pH, ammonia, nitrite, and nitrate levels.
For fish to thrive, water must be similar to that which could be found in their natural environment. This means the ammonia and nitrite levels in your tank’s water should be so insignificant as to be undetectable. If your system is set up correctly, nitrate levels should be low, too.
The water’s pH should be neutral, between 6.8 – 7.0. These levels are ideal for fish, plants, and bacteria. The pH of the water in aquaponics systems usually drops below 7.0 once the initial cycle has finished. To raise the pH, you can alternate between adding calcium hydroxide and potassium carbonate to the tank.
Of course, you need to tend to the plants in your system as you would any raised garden bed. Weeds should not be too much of a problem in a good aquaponics system, though.
In a functioning aquaponics garden, the plants get the nutrients they need and the fish get fresh, recycled water. In return, the practical gardener gets organic vegetables for salads and fish for the grill.
Feature Photo Courtesy of Flickr/Mediamatic
